Add GitHub Actions workflow for sandbox image builds

Author: mmerrell

.github/workflows/build-images.yml

@@ -0,0 +1,108 @@
+name: Build and Push Sandbox Images
+
+on:
+  push:
+    branches:
+      - main
+    paths:
+      - "docker/Dockerfile.base"
+      - "docker/Dockerfile.agents"
+      - "exercises/**"
+      - ".github/workflows/build-images.yml"
+  workflow_dispatch:
+    inputs:
+      reason:
+        description: "Reason for manual rebuild"
+        required: false
+        default: "Manual trigger"
+
+env:
+  REGISTRY: ghcr.io
+  BASE_IMAGE: mmerrell/temporal-python-sandbox
+  AGENTS_IMAGE: mmerrell/temporal-python-agents-sandbox
+
+jobs:
+  build-base:
+    name: Build temporal-python-sandbox (base)
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Log in to GitHub Container Registry
+        uses: docker/login-action@v3
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Extract Docker metadata
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ${{ env.REGISTRY }}/${{ env.BASE_IMAGE }}
+          tags: |
+            type=sha,prefix=sha-,format=short
+            type=raw,value=latest,enable={{is_default_branch}}
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Build and push base image
+        uses: docker/build-push-action@v5
+        with:
+          context: .
+          file: docker/Dockerfile.base
+          platforms: linux/amd64
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+          cache-from: type=registry,ref=${{ env.REGISTRY }}/${{ env.BASE_IMAGE }}:buildcache
+          cache-to: type=registry,ref=${{ env.REGISTRY }}/${{ env.BASE_IMAGE }}:buildcache,mode=max
+
+  build-agents:
+    name: Build temporal-python-agents-sandbox
+    runs-on: ubuntu-latest
+    needs: build-base
+    permissions:
+      contents: read
+      packages: write
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Log in to GitHub Container Registry
+        uses: docker/login-action@v3
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Extract Docker metadata
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ${{ env.REGISTRY }}/${{ env.AGENTS_IMAGE }}
+          tags: |
+            type=sha,prefix=sha-,format=short
+            type=raw,value=latest,enable={{is_default_branch}}
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Build and push agents image
+        uses: docker/build-push-action@v5
+        with:
+          context: .
+          file: docker/Dockerfile.agents
+          platforms: linux/amd64
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+          cache-from: type=registry,ref=${{ env.REGISTRY }}/${{ env.AGENTS_IMAGE }}:buildcache
+          cache-to: type=registry,ref=${{ env.REGISTRY }}/${{ env.AGENTS_IMAGE }}:buildcache,mode=max